High Vessel Outlet

ABSTRACT

Embodiments of an outlet tube assembly for use with a dispensing vessel are disclosed. The dispensing vessel has a side wall defining a chamber; the side wall has an upper portion and has a lower portion that tapers downwardly to an outlet. The outlet tube assembly facilitates accurate measurement of a particulate material level within the dispensing vessel and/or reduces contamination of the particulate material.

FIELD

The present disclosure relates to an outlet tube assembly for use with adispensing vessel.

BACKGROUND

A dispensing vessel, such as a hopper, may have a lower portion (e.g., afrustoconical portion) tapering to an outlet for dispensing material,such as particulate material. This arrangement often produces afunnel-type flow pattern, making it difficult to accurately determinethe level of a particulate solid (e.g., a powder or granules) within thedispensing vessel.

An inner metal surface of the dispensing vessel may be a contaminationsource. Metal transfer may occur as particulate material rolls down theinner walls of the dispensing vessel, resulting in particulatecontamination. In certain industries, such contamination may beunacceptable. For example, the silicon purity demanded by industry forapplications in the electronic and photovoltaic industries is extremelyhigh and frequently only materials with trace amounts of contaminationmeasured at the part per thousand level (electronic grade) or part perbillion level (photovoltaic grade) are deemed acceptable. Extreme caremust be taken in any handling, packaging or transportation operations toavoid contamination. At any time the polycrystalline silicon is incontact with a surface, there is a risk of contamination of thepolycrystalline silicon with that surface material. If the extent ofcontamination exceeds certain industrial stipulations, then the abilityto sell the material into these end applications may be restricted oreven denied. In this respect minimizing contact metal contamination is aprimary concern if silicon performance criteria in the semiconductorindustries are to be attained. Thus, it is desirable to minimize contactof the dispensed particulate material with the dispensing vessel walls.

SUMMARY

A dispensing assembly includes a dispensing vessel and an outlet tubeassembly connected to the dispensing vessel. The dispensing vessel has aside wall that defines a chamber suitable to contain particulatematerial, wherein the side wall has an upper portion and has a lowerportion that tapers downwardly to an outlet. In some embodiments, theupper portion of the side wall is substantially vertical. The outlettube assembly includes a tube having an inlet and an outlet in fluidcommunication with the inlet, wherein the tube extends upwardly throughthe outlet of the dispensing vessel, and wherein the tube has asufficient length that the tube inlet is positioned to receiveparticulate material at or above the top of the lower portion of theside wall.

The dispensing assembly may further include a level sensor located inthe chamber. In certain embodiments, the level sensor has a lower endpositioned at a height below the tube inlet. The dispensing assembly mayhave a dispensing vessel inlet, optionally coupled to a particulatematerial source such that particulate material can be transferred intothe chamber via the dispensing vessel inlet. When particulate materialis transferred into the chamber, a stagnant bed of particulate materialis formed.

The outlet tube assembly may include a base having an aperturetherethrough that is dimensioned to receive the tube, wherein theaperture is in fluid communication with the outlet of the tube and thetube outlet is located within the aperture. In some examples, the basehas an outer horizontal dimension greater than or equal to an innerhorizontal dimension of the outlet of the dispensing vessel. In onearrangement, the tube is removably coupled to the base. In otherarrangements, the outlet tube assembly has a unitary construction. Insome embodiments, the base is attached to the dispensing vessel outlet.Optionally, the base is removably attached to the dispensing vesseloutlet.

In some embodiments, at least a portion of an inner surface of the tubecomprises a ceramic, graphite, glass, a martensitic stainless steelalloy, or a microcellular elastomeric polyurethane. In certainembodiments, the tube includes an upper tube portion coupled to a lowertube portion. The upper and lower tube portions may be constructed ofdifferent materials. In some arrangements, the upper tube portioncomprises a ceramic, graphite, glass, or a martensitic steel alloy. Atleast a portion of an inner surface of the upper tube portion and/or aninner surface of the lower tube portion is coated with a microcellularelastomeric polyurethane.

A dispensing assembly for dispensing particulate polysilicon withmitigation of polysilicon contamination includes a dispensing vesselcomprising a side wall that defines a chamber suitable to containparticulate polysilicon, wherein the side wall has an upper portion andhas a lower portion that tapers downwardly to an outlet, and an outlettube assembly comprising a tube having an inlet and an outlet in fluidcommunication with the inlet, wherein the tube extends upwardly throughthe outlet of the dispensing vessel, wherein the tube has a sufficientlength that the tube inlet is positioned to receive particulate materialat or above the top of the lower portion of the wall, and wherein atleast a portion of an inner surface of the tube comprises a ceramic,graphite, glass, a martensitic steel alloy, or a microcellularelastomeric polyurethane coating. In some embodiments, the outlet tubeassembly further comprises a base having an aperture therethrough thatis dimensioned to receive the tube, wherein the aperture is in fluidcommunication with the outlet of the tube and the tube outlet is locatedwithin the aperture. At least a portion of the inner surface of the tubemay comprise silicon carbide, silicon nitride, graphite, quartz, amartensitic stainless steel alloy, or a microcellular elastomericpolyurethane. In some arrangements, the dispensing assembly includes alevel sensor located in the chamber, wherein the level sensor has alower end positioned at a height below the tube inlet.

The foregoing and other objects, features, and advantages of theinvention will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a dispensing vessel.

FIG. 2A is a perspective view of an outlet tube assembly forretrofitting a dispensing vessel.

FIG. 2B is a perspective view of an outlet tube.

FIG. 3 is a cross-sectional view of a dispensing vessel retrofitted withan outlet tube assembly.

DETAILED DESCRIPTION

Dispensing vessels may be used to dispense particulate material throughan outlet in a lower wall, or portion, of the dispensing vessel. In someapplications, it is useful to determine a volume of particulate materialremaining in the dispensing vessel. Many level sensors are commerciallyavailable for use to measure a level of particulate material indispensing vessels. Some sensors detect only whether an upper boundaryof the particulate material is above or below the sensor, which may beattached to a wall of the vessel. Other sensors can measure the level ofthe particulate material by suitable means, for example, RF(radiofrequency) capacitance, RF admittance, conductivity, pressure,magnetic field interactions (magnetostrictive sensor), tuning/vibratingfork, ultrasound, or guided wave radar.

FIG. 1 illustrates one embodiment of a dispensing vessel 100 having aside wall 102 that has a substantially vertical upper portion 104 and alower portion 106 that tapers downwardly to an outlet 108. As aparticulate material 110 flows through outlet 108, a funnel flow patternis established wherein an upper boundary 112 of the particular materialis not substantially horizontal. As shown, the funnel flow patterncreates an upper particulate boundary 112 that is lower above outlet 108than near side wall 102. The funnel flow pattern and ensuing variableupper boundary creates inaccurate readings from level sensor 114. Theinaccuracy is magnified when level sensor 114 is positioned proximateside wall 102 and any portion of upper boundary 112 drops below upperportion 104 of side wall 102. Additionally, as upper boundary 112 dropsbelow upper portion 104, particulate material 110 rolls down lowerportion 106 of side wall 102 as it flows toward outlet 108, enablingincreased contamination of particulate material 110 from contact withside wall 102.

Disclosed herein are embodiments of an outlet tube for retrofitting adispensing vessel to enable an accurate level determination ofparticulate matter within the vessel. The disclosed outlet tube isparticularly useful for a dispensing vessel having a lower portiontapering to an outlet, such as the vessel shown in FIG. 1. In somearrangements, the lower portion has a frustoconical shape.

FIG. 2A illustrates one embodiment of an outlet tube assembly 200.Outlet tube assembly 200 comprises a tube 201 having an inner surface201 a, and an inlet 204 in fluid communication with an outlet 206 (notshown). In some embodiments, outlet tube assembly 200 further comprisesa base 208 including an aperture 210 (not shown) therethrough. Aperture210 is in fluid communication with outlet 206. Base 208 has an outerdiameter greater than an outer diameter of tube 202. In someembodiments, aperture 210 is dimensioned to receive tube 201 so thattube 201 extends partially or entirely through base 208. In an exemplaryarrangement, inlet 204, outlet 206, and aperture 210 have a similardiameter. In the embodiment of FIG. 2A, tube 201 is a vertical tube, orpipe, with a circular horizontal cross-section, and base 208 has acircular, horizontal cross-section with a planar, circular, horizontalupper surface 212 and a planar, circular, horizontal lower surface 214.Aperture 210 extends vertically through the base 208. A person ofordinary skill in the art will understand that tube 201 and base 208 mayhave a cross-sectional shape other than circular, e.g., square,hexagonal, octagonal, etc.

Outlet tube assembly 200 may be constructed of any material, orcombination of materials, that (1) is compatible (e.g., non-reactive)with the particulate material and portions of the dispensing vessel thatare in contact with the outlet tube assembly, and (2) has sufficientmechanical strength to maintain its structural integrity during use.Outlet tube 201 and base 208 may be constructed of the same or differentmaterials.

In one embodiment, outlet tube assembly 200 has a unitary construction.In another embodiment, tube 201 is inserted into an aperture 210 throughbase 208 and secured therein by any suitable means. For example, tube201 may include a plurality of threads (not shown) on a lower portion ofits outer surface cooperatively dimensioned to engage with a pluralityof threads (not shown) on an inner surface of the base aperture 210. Athreaded arrangement allows tube 201 to be removed and/or replaced asdesired. Tube 201 may be replaced, for example, if it becomes damaged orclogged during use. Tube 201 also may be replaced with another tubehaving a different length if desired. Alternatively, tube 201 may besecured within aperture 210 by welding, riveting, or using an adhesive.In yet another embodiment, tube 201 may include a flange (not shown) atits lower end, and the flange may be used to secure tube 201 to base208, e.g., by welding, riveting, or inserting screws through the flangeinto the lower portion, etc.

For some particulate materials, an outlet tube may be a source ofparticulate contamination. As particulate material contacts an outlettube, material contamination transfer (e.g., by galling, erosion,diffusion) can occur. Thus, tube 201 may be constructed of a materialthat is resistant to wear and material transfer when contacted byparticulates, e.g., polysilicon granules. In some embodiments, such aswhen the particulate material comprises polysilicon, tube 201 isceramic, graphite, glass, or a martensitic stainless steel alloy.Exemplary materials for tube 201 include silicon carbide, siliconnitride, graphite, and quartz. Particulate contamination from an outlettube primarily occurs when granules contact an upper portion of thetube, e.g., proximate the tube inlet, as they enter into the tube. Thus,in some embodiments, at least an upper portion of an outer surfaceand/or inner surface of tube 201 comprises a material suitable formitigating contamination, e.g., a ceramic, graphite, glass, or amartensitic stainless steel alloy (i.e., a steel alloy having abody-centered tetragonal crystal structure, and comprising less than 20%(w/w) chromium and less than 6% (w/w) nickel). The upper portion may be,for example, coated with a silicon carbide, silicon nitride, graphite,or quartz.

In some embodiments, tube 201 comprises a lower tube portion 202 and anupper tube portion 203 (FIG. 2B). Upper tube portion 203 is coupled tolower tube portion 202. Lower tube portion 202 and upper tube portion203 have a substantially similar horizontal cross-section. Upper tubeportion 203 is constructed of a material that is resistant to wear andmaterial transfer when contacted by particulate material. In someembodiments, when the particulate material comprises polysilicongranules, upper portion 203 is ceramic, graphite, glass, or amartensitic stainless steel alloy. In certain examples, upper portion203 comprises silicon carbide, silicon nitride, graphite, quartz, or amartensitic stainless steel alloy.

Upper tube portion 203 may be secured to lower tube portion 202 by anysuitable means, including welding, adhesion, or interengaging threadedsurfaces. For example, lower tube portion 202 may include a plurality ofthreads (not shown) on an upper portion of its outer surfacecooperatively dimensioned to engage with a plurality of threads (notshown) on an inner surface of upper tube portion 203. Alternatively,lower tube portion 202 may include a plurality of threads (not shown) onan upper portion of its inner surface cooperatively dimensioned toengage with a plurality of threads (not shown) on an outer surface ofupper tube portion 203. A threaded arrangement facilitates removaland/or replacement of upper tube portion 203. Upper tube portion 203 maybe replaced, for example, with an upper tube portion constructed of adifferent material and/or having a different length.

Particulate contamination also can be reduced or eliminated by coatingan inner surface 201 a of tube 201 with a suitable material. In someembodiments, inner surface 201 a comprises a ceramic, graphite, orglass. When tube 201 comprises lower and upper tube portions 202, 203,an inner surface of one or both portions may be coated.

In certain embodiments, at least a portion (e.g., at least 50% or atleast 75%) of inner surface 201 a is coated with a protective linercomprising a polymer material, particularly a microcellular elastomericpolyurethane. When the particulate material is polysilicon, suitablemicrocellular elastomeric polyurethane may have a bulk density of 1150kg/m³ or less, and a Shore Hardness of at least 65 A. In one embodimentthe elastomeric polyurethane has a Shore Hardness of up to 90 A, such asup to 85 A; and from at least 70 A. Thus, the Shore Hardness may rangefrom 65 A to 90 A, such as 70 A to 85 A. Additionally, the suitableelastomeric polyurethane will have a bulk density of from at least 600kg/m³, such as from at least 700 kg/m³ and more preferably from at least800 kg/m³; and up to 1100 kg/m³, such as up to 1050 kg/m³. Hence, thebulk density may range from 600-1100 kg/m³, such as 600-1050 kg/m³,700-1100 kg/m³ or 800-1100 kg/m³. In one embodiment, the elastomericpolyurethane has a Shore Hardness of from 65 A to 90 A and a bulkdensity of from 800 to 1100 kg/m³. The polyurethane liner typically willbe present in an overall thickness of from at least 0.1 mm, such as fromat least 0.5 mm, from at least 1.0 mm, or from at least 3.0 mm; and upto a thickness of about 10 mm, such as up to about 7 mm, or up to about6 mm. Thus, embodiments of the polyurethane liner may have a thicknessfrom 0.1-10 mm, such as 0.5-7 mm or 3-6 mm.

An exemplary retrofitted dispensing vessel 300 is shown in FIG. 3. Thedispensing vessel 300 has a side wall 302 defining a chamber 303. Sidewall 302 has a substantially vertical upper portion 304 and a lowerportion 306 that tapers downwardly to an outlet 308. Particulate matter310 within dispensing vessel 300 has an upper boundary 312. A levelsensor 314 is positioned within chamber 303. Dispensing vessel 300 mayfurther include an inlet 316 through which particulate material 310 canbe added to chamber 303. Advantageously, inlet 316 is not positionedadjacent to level sensor 314. Dispensing vessel 300 optionally includesa service port 318 in lower portion 306 of side wall 302. Service port318 may be used to remove particulate material 310 from the lowerportion of chamber 303.

An exemplary outlet tube assembly 200 is positioned within outlet 308.Outlet tube assembly 200 includes a tube 201 having an inlet 204 influid communication with an outlet 206, and a base 208 having anaperture 210 therethrough. Aperture 210 is in fluid communication withoutlet 206. Base 208 has an outer horizontal dimension D greater than orequal to an inner horizontal dimension of a lower end 309 of side wall302. Outlet tube assembly 200 is positioned such that tube 201 extendsvertically through outlet 308. Tube 202 has a length L sufficient toextend into dispensing vessel 300 so that inlet 204 is at a height at orabove the top of lower portion 306 of side wall 302.

Advantageously, inlet 204 is positioned at a height at or just slightlyabove the intersection of portions 304 and 306 of side wall 302. Thisarrangement maximizes the usable volume of dispensing vessel 300 whileminimizing or eliminating contamination produced by granules rollingdown lower portion 306 of wall 302.

Outlet tube assembly 200 is secured to dispensing vessel 300 by anysuitable means including, but not limited to, welding, riveting,adhesion, or engagement of threaded surfaces. For example, the base 208of the outlet tube assembly 200 may be welded to lower end 309 of sidewall 302. In one arrangement, one or more fasteners may be used, whereinone end of a fastener is attached (e.g., by welding or riveting) to base208 and the other end of the fastener is attached to an outer surface ofside wall 302. Alternatively, if the outer horizontal dimension of base208 is substantially equal to an inner horizontal dimension of outlet308, and a downward pressure of particulate material 310 on outlet tubeassembly 200 is sufficiently small, the outlet tube assembly 200 may beinserted into outlet 308 and held in place by frictional forces betweenbase 208 and an inner surface of outlet 308. In yet another example, aninternally threaded collar (not shown) may be secured to wall 302 at thelevel of outlet 308. The collar may include a plurality of threads on alower portion of its inner surface that are dimensioned to engagecooperatively with a plurality of threads (not shown) on an outersurface of an externally threaded base 208 or an externally threadedtube 201. A collared arrangement facilitates removal and/or replacementof tube assembly 200 as desired.

With reference to FIG. 3, outlet tube assembly 200 reduces or eliminatesthe funnel flow pattern found in a non-retrofitted dispensing vesselthat has an inwardly sloping lower wall tapering to an outlet, therebyproviding a more uniform upper boundary 312 across a width of chamber303 defined by upper portion 304 of side wall 302. Outlet tube assembly200 also creates a “dead zone” or stagnant region of no particulate flowin a lower portion of chamber 303, thereby producing a stagnantparticulate bed 313 in the portion of chamber 303 defined by lowerportion 306 of side wall 302. The dead zone magnitude can be minimizedby adjusting the length L of tube 201 such that inlet 204 is at or justabove the intersection of lower portion 306 and upper portion 304. Thecombination of a more uniform upper boundary 312 and a stagnantparticulate bed 313 facilitates more accurate level readings from levelsensor 314, in chamber 303.

The stagnant particulate bed 313 also minimizes particulatecontamination from wall 302 of dispensing vessel 300. As particulatematerial fills chamber 303, stagnant particulate bed 313 forms in theportion defined by lower portion 306 of side wall 302. As additionalparticulate material fills chamber 303, granules flow across thestagnant particulate bed 313 as they flow toward inlet 204, therebyhaving little or no contact with wall 302.

Embodiments of the disclosed outlet tube assembly provide a low-costmeans for retrofitting dispensing vessels so that (1) more accuratereadings of a particulate matter level within the dispensing vessel canbe obtained, and (2) particulate contamination from contact with thedispensing vessel is reduced or eliminated. The disclosed outletassembly has utility in many applications where it is desirable toaccurately measure a particulate material level in a dispensing vessel,such as when the dispensing vessel that has a lower portion in which theside wall tapers downwardly to an outlet. In one example, a dispensingvessel having a tapered lower portion may be retrofitted with anembodiment of the disclosed outlet tube assembly when a user desires tomaintain a constant flow of particulate material from the dispensingvessel. The retrofitted dispensing vessel facilitates accurate materiallevel determination by the level sensor and allows the user to adjustthe inflow of the particulate material (constant or batchwise inflow) tomaintain a constant, or substantially constant, rate of outflow from thedispensing vessel. Embodiments of the disclosed outlet assembly alsohave utility in applications where it is desirable to minimize productcontamination. Suitable applications include, but are not limited to,any process wherein a particulate material is transferred from adispensing vessel to another apparatus. Exemplary dispensing vesselsinclude a feed hopper for charging a fluid bed reactor (e.g., apolysilicon fluid bed reactor), a feed hopper for charging a meltingfurnace, and a product storage and transfer vessel.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

We claim:
 1. A dispensing assembly, comprising: a dispensing vessel comprising a side wall that defines a chamber suitable to contain particulate material, wherein the side wall has an upper portion and has a lower portion that tapers downwardly to an outlet; and an outlet tube assembly connected to the dispensing vessel, the outlet tube assembly comprising a tube having an inlet and an outlet in fluid communication with the inlet, wherein the tube extends upwardly through the outlet of the dispensing vessel, and wherein the tube has a sufficient length that the tube inlet is positioned to receive particulate material at or above the top of the lower portion of the side wall.
 2. The dispensing assembly of claim 1, wherein the upper portion of the side wall is substantially vertical.
 3. The dispensing assembly of claim 1, further comprising a level sensor located in the chamber.
 4. The dispensing assembly of claim 3, wherein the level sensor has a lower end positioned at a height below the tube inlet.
 5. The dispensing assembly of claim 1, wherein the outlet tube assembly further comprises a base having an aperture therethrough that is dimensioned to receive the tube, wherein the aperture is in fluid communication with the outlet of the tube and the tube outlet is located within the aperture.
 6. The dispensing assembly of claim 5, wherein the base has an outer horizontal dimension greater than or equal to an inner horizontal dimension of the outlet of the dispensing vessel.
 7. The dispensing assembly of claim 5, wherein the tube is removably coupled to the base.
 8. The dispensing assembly of claim 5, wherein the outlet tube assembly has a unitary construction.
 9. The dispensing assembly of claim 5, wherein the base is attached to the dispensing vessel outlet.
 10. The dispensing assembly of claim 9, wherein the base is removably attached to the dispensing vessel outlet.
 11. The dispensing assembly of claim 1, wherein the dispensing vessel has a dispensing vessel inlet.
 12. The dispensing assembly of claim 11, wherein the dispensing vessel inlet is coupled to a particulate material source such that particulate material can be transferred into the chamber via the dispensing vessel inlet.
 13. The dispensing assembly of claim 12, further comprising a stagnant bed of the particulate material in the chamber.
 14. The dispensing assembly of claim 1, wherein at least a portion of an inner surface of the tube comprises a ceramic, graphite, glass, a martensitic stainless steel alloy, or a microcellular elastomeric polyurethane.
 15. The dispensing assembly of claim 1, wherein the tube comprises an upper tube portion coupled to a lower tube portion.
 16. The dispensing assembly of claim 15, wherein the upper tube portion and the lower tube portion are constructed of different materials.
 17. The dispensing assembly of claim 15, wherein the upper tube portion comprises a ceramic, graphite, glass, or a martensitic steel alloy.
 18. The dispensing assembly of claim 15, wherein at least a portion of an inner surface of the upper tube portion, an inner surface of the lower tube portion, or an inner surface of the upper tube portion and an inner surface of the lower tube portion is coated with a microcellular elastomeric polyurethane.
 19. A dispensing assembly for dispensing particulate polysilicon with mitigation of polysilicon contamination, comprising: a dispensing vessel comprising a side wall that defines a chamber suitable to contain particulate polysilicon, wherein the side wall has an upper portion and has a lower portion that tapers downwardly to an outlet; and an outlet tube assembly comprising a tube having an inlet and an outlet in fluid communication with the inlet, wherein the tube extends upwardly through the outlet of the dispensing vessel, wherein the tube has a sufficient length that the tube inlet is positioned to receive particulate material at or above the top of the lower portion of the wall, and wherein at least a portion of an inner surface of the tube comprises a ceramic, graphite, glass, a martensitic steel alloy, or a microcellular elastomeric polyurethane coating.
 20. The dispensing assembly of claim 19, wherein the outlet tube assembly further comprises a base having an aperture therethrough that is dimensioned to receive the tube, wherein the aperture is in fluid communication with the outlet of the tube and the tube outlet is located within the aperture.
 21. The dispensing assembly of claim 20, wherein at least a portion of the inner surface of the tube comprises silicon carbide, silicon nitride, graphite, quartz, a martensitic stainless steel alloy, or a microcellular elastomeric polyurethane.
 22. The dispensing assembly of claim 19, further comprising a level sensor located in the chamber, wherein the level sensor has a lower end positioned at a height below the tube inlet. 